As communication devices such as portable two-way radios and paging receivers become smaller, the components contained within the devices (i.e. an antenna's RF contact or a power amplifier module, etc.) will tend to be smaller also. For example, the power amplifier may be integrated as an integrated circuit (IC) that is commonly packaged in an IC chip carrier, having very many small contact pads. If flexibility is desired in inserting, removing, and reinserting these components, for testing purposes or actual usage in the communication device, there is a need to connect these components without permanently soldering them on to a printed circuit board (PCB).
Therefore, these certain parts or components such as diodes, power amplifiers, antennas, engaging boards or printed circuitry or printed circuit boards (PCBs) require one or more spring contacts to achieve reliable electrical connection. Spring features provide the flexibility to avoid tolerances build up when manufacturing dimensions are not all perfectly exact. This tolerance problem comes into effect especially when extremely close facing of terminals or contact pads are required. The compliance is also needed to accommodate departures from planarity as is common in high volume manufacturing processes where the contact pads may not be exactly flat.
Accordingly, a compliant, a flexible, or a spring type of contact, terminal, or connector is becoming increasingly attractive for small components. The convention method of electrically connecting such pads of an electronic component being of a miniature size, is to interpose between the electronic component and the printed circuit board, an electrical connector such as a type of conductive elastomer, a pogo pin, a bellows-spring contact or a "fuzz button".
The conductive elastomer is self-explanatory, since it is a type of elastomer that is made conductive by molding plated wires through out the body of the elastomer, and extending these wires to the contact surfaces. The "fuzz button" or "fuzz ball" is a resilient mesh of fine gold or gold-plated wires in a cylinder. However, the "fuzz buttons" or balls are expensive to provide in view of the amount of gold that must be used and their construction is labor intensive.
The pogo pin is an elongated pin containing a head which makes contact with one surface and can be compressed by its connection to a spring within a socket of the pin that is soldered to the printed circuit board. These pogo pins are expensive and a certain amount of height is necessary for the elongated pogo pin. In fact, the length of the compressed pogo pin creates an amount of self-inductance that cannot be minimized to achieve a minimum RF path.
The gold plated miniature metal bellows is like an accordion spring that is also elongated as is the pogo pin. Similarly, its height presupposes a certain threshold of self-inductance.
Another deficiency of the prior art is that conductive elastomers, bellows, pogo pins, "fuzz buttons" and other conventional connectors have no capability of wiping the contact pads that they are to connect upon their engagement of those pads. Thus, they do not provide self-cleaning action. After a moderate number of components are changed or replaced, debris will build up and degrade radio frequency (RF) performance over time if the debris is not cleaned, and the contact must be eventually replaced.
There are other compliant designs which provide one or more spring arms of a contact for flexibility and another portion of the contact provides a short low inductance current path for the current. However, this low inductance path is still not short enough at high frequencies such as radio frequency (RF) or microwave frequency. Additionally, these prior art designs purposely provided for only a single circuit path through the terminal. However, it is to be appreciated that parallel inductance paths will reduce the total inductance even though multiple paths are difficult to implement. The minimum self-inductance requirement was not so stringent for these prior art designs, since they were mainly used for digital switching times in the nano-seconds range. However, as the switching times approach the pico-second range, relating to microwave frequencies and above, the RF path will need to be much shorter.